Candidiasis is a localized mucocutaneous disease caused by species of the yeast-like fungus Candida, most commonly C albicans. It is distributed worldwide in a variety of animals. C albicans is a normal inhabitant of the nasopharynx, GI tract, and external genitalia of many species of animals and is opportunistic in causing disease. Factors associated with candidal infections are disruption of mucosal integrity; indwelling, intravenous, or urinary catheters; administration of antibiotics; and immunosuppressive drugs or diseases. The organism most frequently infects birds (see Candidiasis), in which it involves the oral mucosa, esophagus, and crop. Superficial infections limited to the mucous membranes of the intestinal tract have been described in pigs and foals. Systemic candidiasis has also been described in cattle, calves, sheep, and foals secondary to prolonged antibiotic or corticosteroid therapy. In cats, candidiasis is rare but has been associated with oral and upper respiratory disease, pyothorax, ocular lesions, intestinal disease, and urocystitis. Infections are rare in dogs and horses. However, Candida spp have been considered a cause of arthritis in horses and mastitis and abortion in cattle. Fungemia and Candida peritonitis have been noted in dogs with perforating intestinal lesions after surgery, and mucosal and cutaneous candidiasis has been noted in immunosuppressed dogs and in dogs with diabetes mellitus.
Signs are variable and nonspecific and may be associated more with the primary or predisposing conditions than with the candidiasis itself. Calves with forestomach candidiasis have watery diarrhea, anorexia, and dehydration, with gradual progression to prostration and death. Affected chicks are listless and have reduced feed intake and growth rate. Porcine candidiasis affects the oral, esophageal, and gastric mucosa, with diarrhea and emaciation the most consistent signs.
Gross lesions of the skin and mucosae are generally single or multiple, raised, circular, white masses covered with scabs. The organism can penetrate keratinized epithelium and cause marked keratinous thickening of the mucosae of the tongue, esophagus, and rumen. In birds, the crop and esophageal lesions are white, circular ulcers with raised surface scabs that produce thickening of the mucosa; an easily removed pseudomembrane is common.
Fungal organisms are numerous in proliferating epithelial tissue, and diagnosis can be made by examination of scrapings or biopsy specimens from mucocutaneous lesions. C albicans are ovoid, budding yeast cells (2–4 μm in diameter) with thin walls, or they occur in chains that produce pseudohyphae when the blastospores remain attached after budding division. Filamentous, regular, true hyphae also may be visible. The fungal cells generally are limited to epithelial tissue and rarely extend deeper.
Nystatin ointment or topical application of amphotericin B or 1% iodine solution may be useful in the treatment of oral or cutaneous candidiasis. Amphotericin B, 500 g in 1 L of 5% dextrose, was administered IV, every 48 hr for 24 days and then every 72 hr for 15 days, to successfully resolve arthritis induced by C fumata in a horse. Fluconazole (5 mg/kg/day, PO, for 4–6 wk) was also used to successfully treat disseminated candidiasis in foals. Itraconazole and amphotericin B lipid complex are considered the treatments of choice in dogs, but few cases have been treated.